The ideal flow sampler would capture every particle in the flow for testing. Since this is not practical, samplers that capture a large percentage of the flow are often used; however, these samplers result in a large volume of sample material that must be handled and tested. This method has also been found to be impractical. Multi-stage samples that, in essence, sample the sample are a very effective solution to this problem of producing a small but representative sample from a large, initial sampling.